1. Technical Field
The present invention relates to an actuator, an optical scanner, and an image forming device.
2. Related Art
An optical scanner is known that uses an actuator including a twist vibrator and draws images by optical scanning in a laser printer or the like. For example, refer to JP-A-2004-191953.
JP-A-2004-191953 discloses an actuator including a reflection mirror, a fixing frame to support the reflection mirror, and a pair of springs to link the both sides of the reflection mirror and the fixing frame. Each spring includes a linking portion disposed apart from the reflection mirror, a first spring linking the reflection mirror and the linking portion, and a second spring linking the linking portion and the fixing frame at a side opposite to the first spring.
Such actuator is heated by surrounding temperature or light irradiated to the reflection mirror, for example. As a result, the first spring thermally expands. That is, a pair of the first springs is elongated in the longitudinal direction (a direction, in parallel with a rotation center axis, being apart from the reflection mirror) by thermal expansion.
However, in the actuator disclosed in JP-A-2004-191953, the displacement of each linking portion in a direction, in parallel with the rotation center axis and apart from the reflection mirror, is hindered by the second spring. This causes each first spring to be displaced (e.g. be bent or buckle) from a desired position so as to reduce the deformation due to thermal expansion, and the reflection mirror is displaced in its thickness direction. This displacement results in the rotation center axis of the reflection mirror being shifted. As a result, desired rotation characteristics cannot be achieved.
In addition, when the actuator disclosed in JP-A-2004-191953 is used for an optical scanner, light reflected by the reflection mirror cannot be scanned to a desired position of an object, since an optical path length from a light source to the reflection mirror is changed due to the rotation center axis shift of the reflection mirror. That is, it is difficult to perform a desired scanning characteristic.